Digestive tract of Holopedium with microspheres

Photomicrograph of the mm-long invertebrate, Holopedium. This organism lives in the water column of lakes and feeds on algae, bacteria and detritus suspended in the water. The Holopedium in the picture were used in an experiment to measure feeding rates by introducing latex microspheres into their water, and determining how many were eaten within 10 minutes. The organisms were collected from Yellow Belly Lake in the Sawtooth Mountains of Idaho, USA.